The present invention relates to machines for treating hides, skins or the like, and more particularly to improvements in tanning machines of the type wherein a skin or hide (hereinafter referred to as hide with the understanding, however, that the term is intended to embrace hides as well as skins or sides of dead animals) is treated by a rotary severing tool (also called knife cylinder) while one side thereof bears against the cylindrical or substantially cylindrical peripheral surface of a pressure roller or another suitable back support. Still more particularly, the invention relates to improvements in tanning machines of the just outlined character wherein the severing tool cooperates with a grinding tool which is reciprocable lengthwise or substantially axially of the severing tool along a path which is not a straight linear path.
The commonly owned German Auslegeschrift No. 16 60 098 discloses a tanning machine wherein the grinding tool is mounted directly on a support which is reciprocable lengthwise of the rotary severing tool. The support is elastically deformable with reference to a rigid traverse or crosshead so as to ensure that the width of the nip or gap between the rotating severing tool and the aforementioned pressure roller can vary as considered in the longitudinal direction of the severing tool. This is accomplished by changing the configuration of the severing tool, i.e., by ensuring that portions of the peripheral surface of the severing tool are not true cylindrical surfaces. Such configuration of the aforementioned nip or gap is desirable in connection with the treatment of certain hides, namely, of hides wherein relatively hard portions alternate with softer portions. In many instances, the hide is softer at the sides and is much harder in the middle, it being assumed that the hide is formed in the customary manner, namely, by splitting the carcass at the underside of the neck and thereupon between the front legs and on toward and between the hind legs. When a hide is formed in the just outlined manner, the width of the gap portions which allow for passage of softer portions of the hide is normally greater than the width of those portions of the gap which allow for the passage of harder sections of the hide.
As a rule, the deviation of the path for the grinding tool from a straight line is in the range of a few tenths of one millimeter because the elasticity of parts which carry the grinding tool is necessarily limited, i.e., each such part must exhibit a certain amount of stability which precludes excessive deviations of the width of the gap from an average width.
The aforementioned German Auslegeschrift further discloses a modified machine wherein the grinding tool moves along a partially arcuate path as a result of tilting of its support relative to a guide means. To this end, the support is provided with two rolls which track the non-deformable guide means and with a roller follower which extends into an elongated groove. The configuration of the groove is such that is causes tilting of the support relative to the guide means during certain stages of its movement lengthwise of the severing tool. A drawback of the just discussed modification of the patented machine is that here, too, the extent to which the grinding tool can move at right angles to the axis of the rotating severing tool is in the range of a few tenths of one millimeter. If the extent of radial movement of the grinding tool with respect to the severing tool would exceed such relatively low value, the three-point contact between the grinding tool and its guide means would fail to ensure adequate guidance of the grinding tool while the machine is in actual use.
Owing to aforediscussed slight deviation of the peripheral surface of the severing tool from a true cylindrical surface, the machine of the German Auslegeschrift cannot be used for removal of flesh (fleshing or refleshing) from the inner side of the hide. All the prior machine can do is to serve as an equalizing or shaving machine, i.e., it can perform functions of the type where minor deviations of the path for the grinding tool from a true straight path suffice to properly treat successive hides. However, and as is the case with fleshing or refleshing machines which are used to remove meat from the inner side of the hide and wherein the gap between the severing tool and the pressure roller must exhibit relatively narrow as well as rather wide portions (i.e., where the difference between the maximum and minimum widths of the gap is more than one or more tenths of one millimeter), the machine of the German Auslegeschrift is incapable of operating in a satisfactory way. Depending on the condition (nature of treatment) of the hide (e.g., whether or not the hide was treated with lime or for the purpose of increasing its softness), it is often necessary that the difference between the maximum and minimum widths of the gap between the severing tool and the pressure roller be in the range of 2-6 millimeters. The just mentioned difference also depends, at least to a certain extent, on the nature of the hide, e.g., whether the hide is a cowhide, a sheepskin or the hide or skin of another animal.
For the aforementioned reasons, a fleshing or refleshing machine which is used to remove meat from the hide invariably utilizes a cylindrical severing tool and the width of the gap between the severing tool and the back support is varied by deforming the back support. For example, it is known to utilize a back support in the form of a hose which is filled with air or another gas at a given pressure so that it can yield during passage of a hide through the gap between the peripheral surface of such hose and the severing too. It is also known to use a back support in the form of a steel roller whose diameter is sufficiently small to allow for appreciable flexing and attendant changes in the width of the gap between the steel roller and the rotary severing tool. In such instances, the hose and/or the steel roller cannot rotate during passage of a hide through the gap. This presents problems, especially as concerns the extent of wear. Thus, the wear upon the hose or roller as a result of frictional engagement with the hide and/or severing tool is so pronounced that it can lead to undesirable changes in the width of the gap.